In the electrolysis of alkali metal chlorides in diaphragm electrolytic cells, the alkali metal chloride brine is typically fed to the anolyte chamber of the cell. The anolyte liquor is an acidified alkali metal chloride solution typically having a pH of from about 2.5 to about 4.5 and the catholyte liquor solution is typically a strongly basic alkali metal hydroxide-alkali metal chloride solution. For example, in the case of sodium chloride electrolysis, the anolyte liquor is an acidified sodium chloride solution containing from about 125 to about 250 grams per liter of sodium chloride at a pH of from about 2.5 to about 4.5, and the catholyte liquor solution is typically a basic solution containing from about 110 grams per liter to about 145 grams per liter of sodium hydroxide and from about 180 grams per liter to about 215 grams per liter of sodium chloride.
The anolyte chamber of the cell is separated from the catholyte chamber of the cell by an electrolyte permeable asbestos diaphragm.
The diaphragms of the prior art have generally been prepared by depositing chrysotile asbestos on an electrolyte permeable, metal cathode by inserting the cathode assembly in a liquid composition of chrysotile asbestos and imposing a reduced pressure within the cathode assembly whereby to draw liquid composition through the cathode assembly depositing fibrous asbestos on the cathode. The diaphragms obtained in this way, while generally satisfactory, are characterized by a wide range of pore diameters within a given diaphragm. Additionally, the asbestos diaphragms of the prior art are characterized by non-uniformity of thickness, fiber orientation and the like.